Onsite or Offsite Welding Repair Work on Exotic Metals
VJIKKS ENGG POWER (M) SDN BHD
Heat Exchangers, Titanium, Tantalum
Welding work on Exotic metals like Titanium,Tantalum,Zirconium,Niobium etc.,
has to be done by the well trained personnel and by following strict procedures.
For example a few important points related to welding on an exotic metal Tantalum:
-Tantalum must be welded to itself and certain other metal by resistance welding and to itself by Inergas arc welding.
-Acetylene torch welding is destructive to the metal.
-Because its melting point is 2700deg F higher than that of SAE1020 steel and its resistivity is only two thirds that of SAE1020 steel, tantalum requires a higher power input to accomplish a sound weld.
-The weld duration should be kept as short as possible in the range of one and ten cycles ( 60cps) to prevent excessive external heating.
-Where possible, the work should be flooded with water for cooling and reduction of oxidation.
- RWMA Class 2 electrodes are recommended with internal water cooling.
-The electrode contours should be kept of constant area and contour to prevent lowering of current and pressure densities.
- A common mistake in welding tantalum is to apply too much elctrode force which causes so little interface resistance that no weld is made.
- Extreme care must be taken to cover with an inert gas all surfaces which are raised above 600deg F by the welding heat.
- Helium,argon or a mixture of the two gases creates an atmosphere which prevents embrittlement by absorption of oxygen,nitrogen or hydrogen into the heated metal.
- Extremely high ductility can be obtained in welding chamber which can be evacuated and purged with inert gas.
- Where the use of a welding chamber is not practical,the heated surfaces can be protected by proper gas backed fixturing.
, Heat Exchangers